Color tube screening apparatus



May 16, 1967 -r HAJDUK ETAL COLOR TUBE SCREENING APPARATUS 3 Sheets-Sheet 1 Filed Jan. 26, 1966 May 16, 1967 J HAJDUK ET AL 3,319,759

COLOR TUBE SCREENLNG APPARATUS Filed Jan. 26. 1966 5 Sheets-Sheet 2 M: I {O 53 \INVENTURS N Thaddeus J Hojduk 5| 54 O", Raymond J. Pekosh 50b 50a 35 Ba y Aftor May 16, 1967 HAJDUK ET AL 3,319,759

COLOR TUBE SCEFENING APPARATUS Filed Jan. 26. 1966 3 Sheets-$heet 5 INVEN'IORS Thaddeus J. H0 'duk Raymond \J P osh ATTorn United States Patent G 3,319,759 COLOR TUBE SUREENING APPARATUS Thaddeus J. Hajduk and Raymond J. Pelkosh, both of (Chicago, lilh, assignors to The Rauland Corporation, Chicago, lIlL, a corporation of Illinois Filed Jan. 26, 1966, Ser. No. 523,164 Claims. (Cl. 198-19) The present invention is directed to improvements in apparatus for screening cathode ray tubes, especially those for producing images in simulated natural color.

One well known process for the production of color cathode ray tubes in commercial quantities features what is referred to as slurry screening. In practicing that process, a slurry coating of a photosensitive resist and one of the three color phosphors is applied over the image or screen area of the picture tube. After the coating is dried, it is exposed to actinic light through the shadow or aperture mask of the tube in process. As a consequence of this exposure, elemental areas of the coating are rendered insoluble and the pattern thus established is developed by washing the exposed screen with a solvent, preferably water. The exposed elemental areas constitute the triad elements of the particular color in process.

This procedure is followed for each of the three colors with appropriate adjustment in position of the exposing light source for each phosphor to the end that the color phosphor dots are properly interspersed in the now familiar dot triads of the color mask tube.

Screening apparatus for carrying out this sort of process is described and claimed in the copending application of Joseph Fiore, Ser. No. 391,864, filed Aug. 25, 1964, and assigned to the assignee of the present invention. In the Fiore apparatus the slurry process for any single phosphor is carried out in a screening machine that has a series of work stations disposed along a closed path. An endless conveyor extending along that path supports a plurality of screening carts each of which accommodates a single tube screen under process. The screen is held in a workholder of the cart which also has a complete motor driving system for rotating the workholder at a selected speed. In addition to being rotated, the workholder is subject to being tilted to various angles advantageous to the several processing steps, the tilting being accomplished by means of a tilt rail extending along the conveyor and engaged by a pair of guides extending from the workholder and projecting on opposite sides of the tilt rail.

That apparatus has performed satisfactorily and the present invention is a further development of this approach to automating slurry screening. It features screening carts traveling with a conveyor past a series of work stations and differs from the Flore apparatus in that a motor is installed at each work station in which the screen is to be rotated. This has the advantage that the process step at each such station always takes place at the same speed and avoids difiiculties of speed variations from motor to motor when the driving motor is integral with the screening cart.

Accordingly, it is an object of the invention to provide an improved cathode ray tube processing apparatus having a multiplicity of Work stations and characterized by an improved driving arrangement assuring that the speed of rotation of the tube under process is always the same at a given work station.

It is a further specific object of the invention to provide in apparatus of this type additional flexibility in permitting not only rotational but also tilting motion of the workholder under the control of motors installed at certain of the work stations.

Apparatus in accordance with the invention for processing a cathode ray tube comprises an endless conveyor ice extending along a reference path. Indexing means effect step-by-step movement of the conveyor between a plurality of work stations disposed along that path. There are a plurality of carts secured to the conveyor to be presented seriatim to the work stations and a rotatable workholder is mounted on each cart to support the tube in process. There is a drive system on each cart for rotating the workholder and terminating in a driven clutch element. A driving motor and a driving clutch element are provided in a number of the work stations, individually movable between a rest position in which the driving clutch element is clear of the path of movement of the driven clutch elements and a work position in which the driving clutch element engages the driven clutch element of the workholder instantaneously at the assigned one of the work stations. Finally there are means, independent of movements of the conveyor, for concurrently displacing the driving motors and driving clutch elements between their rest and work positions in timed relation to the indexed movement of the conveyor. That is to say, the conveyor indexing and engaging of the clutches do not occur simultaneously; rather in timed sequence.

At one or a small number of the work stations there is provided an additional driving motor and driving clutch element for cooperating with the driven clutch element of a second driving system provided on the screening carts. This second driving system is arranged to displace the workholder about a tilt axis which is normal to the axis of rotation of the workholder. The feature of motor controlled tilting is advantageous at the dispensing station to facilitate distributing the slurry as a coating over the entire area of the screen in process. It may also be employed beneficially in the reclaim station where the excess of slurry is dumped from the screen after a sufficient coating has been applied.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which:

FIGURE 1 is an elevational view of a cathode ray tube screening apparatus embodying the subject invention;

FIGURE 2 is a sectional plane view taken along line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary view taken along line 33 of FIGURE 2;

FIGURE 4 is a fragmentary view taken along line 44 of FIGURE 3;

FIGURE 5 is a detail view taken along line 55 of FIGURE 3 to illustrate the coupling of the motors of one station with an actuator for displacing those motors between rest and work positions;

FIGURE 6 is a fragmentary view taken along line 6-6 of FIGURE 3 to show the details of the removable section of the tilt rail of the screening apparatus; and

FIGURES 7 and 8 are enlarged fragmentary views to illustrate screening carts and a multi-track cam and cam follower assembly which actuates and times functions of the apparatus.

Present-day shadow mask type color cathode ray tubes have envelopes of two principal parts. One part is the cap which is much like a flanged dish with the dish correspending to the image or screen area. The other part is generally funnel shaped and its large end corresponds in dimension and configuration to the cap in order that they may be joined through a frit sealing operation. In crosssection it is immaterial whether the tube be round or rectangnilar; either may be processed by the apparatus under consideration.

As illustrated in FIGURE 2 the apparatus is generally circular and comprises an endless or circular conveyor extending along an annular reference path. A plurality of screening carts 11 are secured to the conveyor so that as the conveyor is indexed to move in step-by-step fashion past a multiplicity of work stations the several carts are presented to those stations seriatim. Basically, the screening apparatus is generally similar to that of the Flore application to which reference may be had for details of the various process steps and the controls necessary for conducting the assigned work function at each of the several stations. The present invention has to do most particularly with structural details of the conveyor, its screening carts, and driving systems which Will be described more fully hereafter. Preliminarily, however, a functional review of the overall apparatus will be given.

For convenience the lettered circles in FIGURE 2 identify specific work stations and the following table assigns for each such station the process step to take place there, the tilt angle of the tube screen relative to vertical as presented to that station and the speed of rotation of the screen about its central axis While the screening cart is in the particular station.

The crosshatched enclosing outline of FIGURE 2 represents the housing of the screening machine which encloses the conveyor. It is desirable that the enclosing partitions be transparent to permit observation of work in process. Preferably the housing is interrupted at stations A and H in order that an operator may have access to the workholder of the screening carts at these stations.

In describing the operation of the apparatus it will be assumed initially that conveyor 10 is at rest permitting an operator to load a screen panel 9 on the workholder of the screening cart instantaneously at station A. Generally, the cart is equipped also to accept the aperture mask 9a (FIGURE 1) assigned to that particular panel as they are intended to traverse the entire screening functions together. After the panel and its mask have been loaded onto the cart, a programmer indexes the conveyor and steps the panel under process to station B where the panel is washed with a water spray as it is rotated by its workholder. After the washing cycle has been completed, the conveyor indexes again, presenting panel 9 to station C where it is further rinsed. As the panel traverses stations D, E and F it is dried by heaters located in those stations. At stations G and H the panel may be inspected and cooled. If a defect is observed, it may readily be removed at station H; otherwise it continues through the machine.

At station I a quantity of phosphor slurry is discharged into the panel while the panel is in essentially a horizontal plane traveling at 15 r.p.m. A measured amount of slurry is dispensed and it begins to puddle or spread out over the screen. After the slurry has been dispensed but still within the index period within the conveyor, the panel 9 is tilted by tilting the workholder from horizontal to a tilt position of about 15 while the rotation of the workholder continues uninterruptedly. This augments dispersion of the slurry to assure a uniform coating over the entire panel.

At the end of this part of the screening program, the conveyor indexes the panel in process to station I where excess slurry is reclaimed. If the panel is round, the reclaim may be conveniently accomplished by rotating the panel at the speed of 60-90 rpm. and by inserting a probe to extract the excess slurry. Another type of reclaim, however, is useful whether the panel be round or rectangular. This is known as dumping and features further tilting of the workholder to an angle of so that the slurry pours out of the panel into a reclaim receptacle or fixture. If the panel is rectangular, its rotation may be stopped during the actual dumping step in which case a monitor is provided so that a corner of the panel is lowermost at that time in order that the slurry may pour over the corner rather than over studs that are usually provided, extending inwardly from the flange of the panel, as mounting devices to which the aperture mask is affixed when that'mask is to be positioned in operative relation to its screen. If dump reclaim is used, a tilt motor is provided at station I as well as at station I as: indicated in FIGURE 2. For probe reclaim, the tilt motor is omitted from station I and only one motor will be at that station, namely the motor rotating the panel in process. From station I the panel is indexed successively to stations K and L where it is trimmed by a water spray which removes slurry from the flange of the panel and it is also dried at these stations. Further drying is accomplished in stations M and N. In station 0 the panel is cooled and from here it is delivered to station A where: it is removed.

It is preferable that a sensing system be installed in stations B and I to determine whether or not the work-- holder instantaneously in such stations does in fact carry If not, the sensing system arranges that the various work functions are not performed as the cart: without a panel traverses the several work stations. A. suitable sensing arrangement is the subject of copending' application, Ser. No. 392,010, filed Aug. 25, 1964, in the name of Raymond J. Pekosh and assigned to the present.

a screen panel.

assignee.

containing a particular phosphor.

posed through aperture mask 9a of panel 9 in process and' the exposed panel is then loaded on a similar machine- In this second screening machine the process steps up tostation I, which is the dispense station, develop the ex- The dispense station at this second machine applies a coating of' a different phosphor and it is processed in generally the same way except that the panel with its second coating, when delivered to the next light house, has a specifically different series of elemental areas exposed since these:

posed dots of the previously applied phosphor.

areas are to distinguish from the exposed areas of the first coating. is removed from the light house and delivered to the third. such screen machine. In this machine the exposed portions of the second coating are developed and a third phosphor coating is applied. It is exposed in turn and' delivered in essentially the same way to still another or fourth screening machine which is the same in structure and operation as that illustrated and described. Instead of dispensing a phosphor slurry, this fourth machine may apply a film coating to the screen which will now have received its pattern of three-color phosphor triads. The screen is then ready for aluminizing which is of no concern here.

It is appropriate now to consider the structural features of the screening machine but with particular emphasis only on those portions as to which a claim of invention is here made.

The panel with its exposed second coating The machine has a base or frame work which supports the housing 16 and the movable components. As indicated above, the housing has transparent panels at most of the work stations and there is a concentric inner member 17. At the top of the machine there is a plenum 18 supplied from a conventional source of conditioned air (not shown) by means of an input conduit 20. At stations I and I there is an absolute or exceeding by fine air filter 19 leading from plenum 18 to the channel defined by members 16 and 17. An exhaust duct 21 serving these two stations permits the establishment of laminar air flow vertically downwardly as shown by the arrows in FIG- URE 1 across the tube panel 9 in process. This is done in order that a condition of optimum cleanliness may be obtained at these screening stations. The feature of laminar air flow at screening stations is described and claimed in an application of Fiore et a1., Ser. No. 391,985, filed Aug. 25, 1964 and assigned to the assignee of this invention. At the remaining work stations, especially those where the panel has been tilted to an angle of 130, the air flow is not laminar since this refinement is not there required. As indicated at the right side of the machine in FIGURE 1, for these stations the air travels downwardly through a channel 22 to a filtering and heating section the temperature of which is subject to a control 23. The heated and filtered air is directed upwardly to the face of the panel and exhausts at the top of the machine in the manner illustrated.

Conveyor The conveyor 10 is circular and its principal structural component, as indicated in FIGURE 3, is a fiat ring which may carry on its under surface one or more rails 25 which rest on and are guided by vertical and horizontal rollers 26, 26a disposed along an annular path on machine frame 15 so that the conveyor may be easily rotated or moved along a circular path.

Movement of the conveyor is under the control of indexing means which effect a step-by-step movement to displace the conveyor from one work station to the next in the screening machine. Indexing is under the control of a principal driving motor 3t (FIGURE 1) which is coupled by means of a single revolution clutch 31 to a multi-track cam and cam follower assembly 32. Referring to FIGURE 8, it is seen that assembly 32 carries on an upper surface an upstanding roller 32a. A series of cooperating cam tracks 33, dimensioned to receiver roller 32a, are disposed about conveyor 10 extending radially of the machine from the lower surface of the conveyor.

The at rest position of cam assembly 32 is indicated in FIGURE 7 and its rotation is counter-clockwise. When clutch 31 is engaged under the control of a conventional programmer or timer (not shown), the first 90 of cam rotation presents follower 32a to one of cam tracks 33. Continued rotation of assembly 32 causes roller 32a to enter cam track 33 and displace conveyor 10 counterclockwise. The radial dimension of track 33 is such that follower 32a remains within the track for most of the rotation of cam assembly 32. Near the end of the single revolution, perhaps after 270, roller 32a will have moved conveyor 10 one complete step and it will then exit from track 33 and return to the rest position of FIGURE 7.

Screening carts When the machine is equipped with a full complement of carts, there are the same number of carts as work stations. The structure of the carts is best illustrated in FIGURES 3 and 7. Each cart has a casing or housing 49 removably secured to conveyor 10 by machine bolts, so that as the conveyor is indexed the carts are presented seriatim to the several work stations of the machine. Each cart carries a vertically extending frame 400 for carrying the mask 9a assigned to the tube panel 9 in process and a workholder 41 for removably supporting tube panel 9.

Each holder has a central hub from which three radially,

extending arms project to define a spider for receiving the 6 panel. One arm is equipped with a clamp (not shown) removably locking the panel within the workholder as disclosed in application Ser. No. 391,985.

As clearly illustrated in FIGURE 7, a stub shaft 42 is rotatably supported from housing 4% so that the workholder may be rotated about the axis of that shaft. There is an incomplete drive system on the car which, when completed, will cause the workholder and panel to rotate. This includes the system of gears and shafts 43 which terminates at the inner side of the screening cart in a driven clutch element or socket 43b.

In addition to being rotatable, workholder 41 is supported for tilting about a tilt axis normal to the axis of rotation. For that purpose housing 40 has a section 40a that may rotate about stub shaft 43a on one side and about a stub shaft 44a on the other side. There is a second incomplete drive system 44 on the cart for driving the workholder about its tilt axis which includes the axis or" shafts 43a and 44a. This drive has a series of gears and shafts generally similar to that of system 43 and likewise terminates in a second driven clutch element or socket 44b.

In addition to the provision for a motor controlled tilt of the workholder, there are pairs of guide rollers 45 extending from housing portion 40a as illustrated in FIG- URE 3. It is the purpose of these guides to straddle a tilt rail 12 which extends along the path of the conveyor as clearly shown in FIGURE 2. Engagement of the tilt rail by guides 45, in conjunction with the configuration of the tilt rail, causes the workholder and the panel which it supports to assume a desired angle of tilt as the conveyor steps the screening cart from one work station to the next. For the most part, the guide rail not only determines the til-t or angular orientation of the workholder but restrains the workholder in a chosen angular position in most of the Work stations. Obviously where the tilt drive system of the screening cart is to be effective, it is necessary to release the restraining effect of the tilt rail. That purpose is served by providing a removable section 12a for the rail as indicated in FIGURE 6. This section is located not only at the work stations of the machine for which it is desired to have a motor driven tilting of the workholder but also in such position that the movable rail section 12a is received between the lower most guides 45 and the workholder of the cart in that particular station as indicated in FIGURES 3 and 6.

The movable rail section 12a is at the free end of a pivoted bell crank 48 which is connected by a linkage 49a to the piston shaft of an air cylinder 49 having the usual input and exhaust lines to admit and control the position of the piston. The at rest position of FIGURE 6 shows link-age 49a to be holding movable rail section 12a in such a position that it serves as a continuation of tilt rail 12. When air is admitted to cylinder 49, displacing its piston to the left, linkage 49a straightens and rotates bell crank 48 clockwise about its pivot to displace movable r-ail section 12a to its dotted-line position in which it is free of guide pins 45 of the screening cart.

A convenient method of maintaining the described structure, as seen in FIGURE 6, is to flatten a portion 12b of tilt rail 12 and to have mounting bolts for the housing of the air system including cylinder 49 accommodated by the fiat rail segment.

It is clear that if workholder 41 is tilted, after having been released for such displacement by the removal of rail segment 12a, guides 45 no longer are in alignment with tilt rail 12. As indicated in broken-construction line in FIGURE 3, the maximum displacement of Workholder 41 is determined by the engagement of guides 45 with a stop 40b which is suitably supported by the machine frame. This position is one in which guides 45 are in alignment with the next succeeding section of the tilt rail so that as the conveyor is indexed and the screening cart moves out of the illustrated station, it is properly guided by the tilt rail, being retained in the angular position shown in the broken lines of FIGURE 3.

Driving motors The driving motors here under consideration are those relied upon to complete the driving systems of the screening carts which, as previously described, are incomplete for want of a power source. Obviously, since there are two partial drive systems on each screening cart it is contemplated that there is a need for two driving motors in at least one work station. In most work stations there is but a single driving motor, namely, that which is required to energize the driving system for rotating the workholder about the axis of its shaft 42. Such a motor 50 is shown in FIGURES and 7. It is equipped with a speed reduction system 50a and terminates in a driving clutch element 5% which is a disc or cone structure proportioned to be received within the socket type driven clutch termination 43b of drive system 43 of the screening cart. Preferably, clutch element 50b is mounted on springs which circumscribe a pair of mounting pins to the end that there is a floating mount that facilitates complete entry of the driving clutch element within the driven clutch or socket 43b. A motor of this type is provided in which each of the work stations where in the preceding table it is indicated that the workholder is rotated.

Each such motor is movable between a rest position in which its driving clutch element is clear of the path of movement of the driven clutch elements of the screening carts and a work position in which the driving clutch element of the particular motor engages the driven clutch element of the workholder instantaneously at the location of the particular driving motor in question. As shown in FIGURE 5, motor 50 is supported on a plate 51 which in turn rides on a pair of slide rails 52. These rails rest in a support structure 52a which is secured to frame 15 of the machine as indicated in FIGURE 3.

There are means, independent of movement of conveyor 10, for concurrently displacing driving motors 50 with their driving clutch elements 5% between their rest and work positions in timed relation to the indexed movement of the conveyor. As shown in FIGURE 2, there is a circular actuator 53 disposed concentrically of and inside conveyor 10. This actuator as shown in FIGURES 5 and 7 is coupled by means of links 54 to motor carriages 51, there being one such link for each motor carriage. The motor displacing system further includes means for oscillating actuator 53 so that when the actuator has been displaced to its most counterclockwise position shown in FIGURE 5 motor carriages 51 will have been retracted to their rest positions.

Alternatively, when the actuator shall have been displaced to its clockwise position links 54 will have advanced the several motor carriages, motors and driving clutch elements to their work positions of FIGURE 7 in which all clutches will have become engaged to complete the driving system of the screening carts associated with the various driving motors at that particular time. Oscillation of actuator 53 is under the control of a cam track 32b (FIGURE 8) cut in the under surface of assembly 32 and a cam following roller 54a which is carried on the free end of an arm 54b secured to a vertically extending shaft 54. A link 54c secured to shaft 54 above the surface of conveyor 10 connects to actuator 53 as indicated in FIGURE 7 to the end that oscillation of shaft 54 by the coursing of follower 54a in cam track 32b oscillates actuator 53.

In at least one station of the screening machine, particularly dispensing station I, there is need for a tilt motor and such a motor 60 is shown in FIGURE 5. It is very similar to motor arrangement 50 having a reduction gear system 60a and terminating in a driving clutch element 60b. It is likewise carried by a plate 51a that is secured to carriage 51. As a consequence, displacement of carriage 51 in the manner described above advances the motor system whether it includes a single motor 50 as in most stations or a pair of motors 50 and 51 as at the slurry dispensing station.

Sequence of indexing steps Inasmuch as the engaged clutches mechanically couple the screening carts to driving motors 50, 60 when the latter are in their work positions, it is necessary to release this connection before indexing takes place because the motors are supported on the stationary frame 15 of the machine. This timing is accomplished by the orientation of cam track 32b of assembly 32 relative to the, in effect, lost motion travel of cam follower 32a in approaching the entrance of a cam track 33. In the interval of travel before follower 32a reaches cam track 33, the displacement of cam 32]; rotates shaft 54 counterclockwise, displacing actuator 53 in the same direction and retracting all motors 50, 60 to their rest positions. This frees the driving and driven clutch elements from one another and their release conditions conveyor 10 for its next step movement. The movement of conveyor 10 under the control of cam follower 32a and cam track 33 as previously described takes place while actuator 53 retains motors 50, 60 in their rest position. During the final approximately of travel of cam follower 32a, after it has left cam track 33, there is a corresponding displacement of cam track 32b which is contoured so that in this angular displacement of assembly 32 actuator 53 is displaced in a clockwise direction and motors 50, 60 are returned to their work positions in which they complete their driving connections with the driving systems of each of the screening carts to which driving motors are presented. In other words, the motors are advanced to the work positions after the conveyor has been displaced from one station to the next.

It is desirable that the conveyor be locked against movement during intervals which intervene its successive indexing steps. This also is accomplished by means of a track of cam assembly 32. This is the track 320 formed in the upper face of assembly 32 and, as shown in FIGURE 7, spanning slightly less than As most clearly shown in FIGURE 3 there is a cam roller 33a depending from conveyor 10 at the leading edge of each cam track 33. When cam assembly 32 is in the rest postion of FIGURE 7, follower 33a is lodged midway of track 32c locking the conveyor against further displacement. In the initial 90 travel of cam assembly 32, as follower 32a approaches cam track 33, cam track 320 rotates and follower 33a recedes therefrom as required to free the conveyor for its indexed movement. When the indexed movement has been accomplished, follower 33a is presented at the entrance of cam track 320 so that the final displacement of cam assembly 32 in each single revolution of its movement restores follower 33a into the position of FIGURE 7, once again to lock the conveyor against movement.

Mention has been made of the programming of the machine which, of itself, constitutes no part of the present invention. It will be clear, however, that the work functions conducted at the several work stations should be permitted to take place only in the interval between the indexed movement of conveyor 10 and this is the role of the programming system. Cam assembly 32 has a peripheral cam section 320. which, as illustrated in FIGURE 7, displaces a switch actuator 65 in the rest position of assembly 32. Switch 65 is part of the programming system and causes its cycle to be instituted after indexing has been completed. Each program cycle may terminate under the master control of the system or under shut-off switches provided at individual work stations.

A further timing consideration involves the energization and deenergization of motor 60 which causes motor driven tilting of workholder 41 at the dispense station. The function of tilting in the dispense station is to facilitate distributing a charge of slurry across entirety of panel 9. Accordingly a local programmer is energized when the screen cart is indexed into the dispense station to cause a measured charge of slurry to be dispatched into the panel While it is essentially horizontally disposed. FIGURE 3 shows the dispense station with a conduit 70 through which a charge of slurry may be dispensed. Of course, dispensing should occur only if there is a tube panel in the workholder of the screening cart instantaneously at that station. To that end a probe 71 may sense the presence or absence of a tube panel and interrupt the dispense cycle if it is determined that no panel is in position to receive the slurry charge. A sensing system suitable for this purpose is described and claimed in the aforesaid application of Raymond J. Pekosh Ser. No. 392,010. As previously indicated, it is installed at stations Band I and is shown in FIGURE 3 only as a matter of convenience.

If a .panel is present to receive the slurry charge, the programmed cycle at the dispense station proceeds and slurry is deposited in the panel under process. At about the same time the programmer will have actuated air cylinder 49 and caused rail segment 12a to be removed, freeing workholder 41 for tilting movement. Finally the programmer energizes motor 60 which will have been mechanically coupled to the screening cart in the dispense station to drive the workholder about its tilt axis. Of course, previous to this time and prior to the deposit of the slurry charge motor 50 will have been energized and the workholder will have been placed into rotation; the rotating and tilting motions continue until the tilting motion is arrested when the workholder attains the dotted line position of FIGURE 3. In this position, stop 40b will have interrupted tilting motion and microswitch 65a will have been actuated by guide 45 of the housing 40 to interrupt energization of tilt motor 60. At this time rotation of the tilted panel continues for the remainder of the program cycle and distributes the slurry charge over panel 9.

In the prescribed screening arrangement, the indexed movement of conveyor 10 is independent of the movement of actuator 53 which provides highly desirable flexibility to the screening machine to facilitate, for example, having individual motors at each work station and speed controls mounted on vertical supports at the external periphery of the machine so that adjustment of the operating speed at each station is under convenient control of the operator. There is a distinct advantage in that each cart is driven from the same motor in a given work station and therefore the operations on the tube panels at each station always occur at a given rotational speed. Additionally, it is convenient with this screening machine to have a tilt motor so that tilting and other driving arrangements of the screening carts may be accomplished independently of the movement of the conveyor. The tilt rail 12, which has been known previously in the art, is elTective for determining the tilt or angular orientation of the workholder as the screening carts travel with the conveyor but it obviously cannot change that relation when the conveyor is at rest. This precludes tilting during the dispensing cycle as an aid in coating so long as tilting depends on relative movement of the screening cart and the rail. The subject invention obviates that limitation of previous screening machines.

Preferably, driven clutch elements 43b and 44b are keyed to the shafts of the driving systems carried by the carts and the gear ratios thereof are 1:1. As a consequence, one may conduct sensing of the driven clutch elements to arrest the workholders at an intermediate tilt position or to interrupt rotation of the workholder at some desired rotational orientation. The latter is material for dump reclaiming for which the rectangular screen panel should be stopped to dump excess slurry over a corner as described above.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

We claim:

1. Cathode-ray tube processing apparatus comprising:

an endless conveyor extending along a reference path;

indexing means for effecting step-by-step movement of said conveyor between a plurality of work stations disposed along said path;

a plurality of carts secured to said conveyor to be presented seriatim to said work stations;

a rotatable workholder on each of said carts for supporting a tube in process;

a drive system on each of said carts coupled to said workholder and terminating in a driven clutch element;

a driving motor and a driving clutch element in at least some of said work stations, individually movable between a rest position in which said driving clutch element is clear of the path of movement of said driven clutch elements and a work position in which said driving clutch element engages the driven clutch element of the workholder instantaneously at the assigned one of said work stations;

and means, independent of movement of said conveyor, for concurrently displacing said driving motors and driving clutch elements between their said rest and work positions in timed relation to the indexed movement of said conveyor.

2. Cathode-ray tube processing apparatus in accordance with claim 1 in which said means for displacing said motors retracts said motors to said rest position before said indexing means steps said conveyor and advances said motors to said work position after said indexing means has stepped said conveyor.

3. Cathode-ray tube processing apparatus in accordance with claim 1 including means for locking said conveyor against movement during operating intervals in which said driving motors are in said Work position.

4. Cathode-ray tube processing apparatus in accordance with claim 3 in which said indexing means, said means for displacing said motors, and said locking means share a common multi-track cam and cam-follower assembly.

5. Cathode-ray tube processing apparatus in accordance with claim 1 in which each of said driving motors is mounted for sliding movement between said rest and work position and in which said means for displacing said motors comprises an actuator concentric with said conveyor, linkage connecting each of said motors to said actuator and means for oscillating said actuator to slide said motors between their aforesaid positions.

6. Cathode-ray tube processing apparatus in accordance with claim 1 in which each of said workholders is supported for tilting about a tilt axis normal to the axis of rotation of said workholders; in which each of said carts has a second drive system terminating in a second driven clutch element and coupled to drive said workholder about its tilt axis; and further in which there is a second driving motor and driving clutch element in one of said work stations movable with the other driving motor and driving clutch element of said one station to engage said second drive clutch element and complete said second drive system.

7. Cathode-ray tube processing apparatus in accordance with claim 6 including means for energizing said second drive system in timed relation to the energizing of said first drive system.

8. Cathode-ray t-ube processing apparatus in accordance with claim 7 including means for restraining said workholder against movement about said tilt axis and means for releasing said restraining means prior to the energizing of said second drive system.

9. Cathode-ray tube processing apparatus in accordance with claim 8 including means for deenergizing said 1 1 second drive system after said workholder has been displaced a predetermined amount about said tilt axis.

10. Cathode-ray tube processing apparatus in accordance with claim 8 in which said workholder restraining means comprises a rail extending along the path of said conveyor having a removable section located at said one work section and guides extending from said workholder on opposite sides of said rail to determine the angular position of said workholder about said tilt axis; and in which said releasing means comprises means for selectively removing said movable section of said rail.

References Cited by the Examiner UNITED STATES PATENTS 2,693,872 11/1954 Baader 198-33 3,216,550 11/1965 Cox 198--33 EVON C. BLUNK, Primary Examiner. RICHARD E. AEGERTER, Examiner. 

1. CATHODE-RAY TUBE PROCESSING APPARATUS COMPRISING: AN ENDLESS CONVEYOR EXTENDING ALONG A REFERENCE PATH; INDEXING MEANS FOR EFFECTING STEP-BY-STEP MOVEMENT OF SAID CONVEYOR BETWEEN A PLURALITY OF WORK STATIONS DISPOSED ALONG SAID PATH; A PLURALITY OF CARTS SECURED TO SAID CONVEYOR TO BE PRESENTED SERIATIM TO SAID WORK STATIONS; A ROTATABLE WORKHOLDER ON EACH OF SAID CARTS FOR SUPPORTING A TUBE IN PROCESS; A DRIVE SYSTEM ON EACH OF SAID CARTS COUPLED TO SAID WORKHOLDER AND TERMINATING IN A DRIVEN CLUTCH ELEMENT; A DRIVING MOTOR AND A DRIVING CLUTCH ELEMENT IN AT LEAST SOME OF SAID WORK STATIONS, INDIVIDUALLY MOVABLE BETWEEN A REST POSITION IN WHICH SAID DRIVING CLUTCH ELEMENT IS CLEAR OF THE PATH OF MOVEMENT OF SAID DRIVEN CLUTCH ELEMENTS AND A WORK POSITION IN WHICH SAID DRIVING CLUTCH ELEMENT ENGAGES THE DRIVEN CLUTCH ELEMENT OF THE WORKHOLDER INSTANTANEOUSLY AT THE ASSIGNED ONE OF SAID WORK STATIONS; AND MEANS, INDEPENDENT OF MOVEMENT OF SAID CONVEYOR, FOR CONCURRENTLY DISPLACING SAID DRIVING MOTORS AND DRIVING CLUTCH ELEMENTS BETWEEN THEIR SAID REST AND WORK POSITIONS IN TIMED RELATION TO THE INDEXED MOVEMENT OF SAID CONVEYOR. 